1. Field of the Invention
The present invention relates to a fastener design, particularly to a screw.
2. Description of the Related Art
Referring to FIG. 1, a conventional screw 1 comprises a shank portion 11, a head portion 12 disposed at one end of the shank portion 11, a drilling portion 13 disposed at the other end of the shank portion 11, and a plurality of threaded units 14 spirally disposed around the shank portion 11. Wherein, the drilling portion 13 is formed into a tapered end. Thus, the screw 1 directly enters an object 2 via the tapered drilling portion 13, and the following threaded units 14 continue entering the object 2 so as to achieve a fastening effect.
Afore screw 1 might be smoothly fastened into the object 2 by means of the drilling portion 13 piercing the object 2. However, in practice, the object 2 is forcedly pierced by the tapered drilling portion 13. Thus, fibers contained in the object 2 are difficult to be severed efficiently. That is to say, the fibers are just simply pushed and thrust by the tapered drilling portion 13, so the screw 1 would be easily impeded by debris resulted from the object 2 in time of drilling. As a result, the debris can not be timely expelled, and the heaped debris incurs an increasing resistance on the screw 1. Thereby, the operation of fastening the screw 1 is influenced.
Referring to FIG. 2, the upright screw 1 in the object 2 might be subject to rustiness since water might pile on the head portion 12. Therefore, in the practical application, the screw 1 is disposed tilting in the object 2. Herein, if the cutting debris can not be timely expelled, the head portion 12 easily bulges out of the object 2 after screwing. Such abnormal operation is unbeneficial for further fastening. Therefore, the screw 1 needs improvements.